In motor-vehicle door latches of this type, typically the motor drive moves the locking lever, which is normally configured as a central locking lever, into locked or unlocked positions. Furthermore, in principle also further positions of the locking lever can be achieved, for example such as the so-called antitheft position.
The unlocking process is generally performed with a keyless entry systems. With such a system the user carries an identification device (for example a code card) that initiates a dialog with a control system provided in the vehicle when the vehicle user approaches the vehicle or actuates the outside door actuating element (the door handle). During the course of this dialog, access authorization of the vehicle user seeking access is verified. Once the authorization has been verified, the control system sends a signal to at least one or all of the door latches of the motor vehicle. Then, the motor-vehicle door latch is unlocked with the help of its drive and can then be opened mechanically, for example with the help of the outside door handle.
The problem with this is that an authorized vehicle user seeking access has often already operated the outside door handle while the dialog is still in process or before the associated motor-vehicle door latch has assumed the unlocked position. The reason for this is that the above-mentioned keyless entry systems require a certain response time to carry out the unlocking operation. This response time includes an activation interval in order to activate the system as the vehicle user approaches, an authorization verification interval and finally the actual actuation interval.
In practice, response times of about 100 msec or more are known, which are perceived by the vehicle users as too long compared to conventional motor-vehicle door latch systems. Furthermore, it is possible that the vehicle user has already operated the outside door handle in an attempt to open it before the associated motor-vehicle door latch has assumed the unlocked position. The vehicle user then has to release the outside door handle and perform another confirmation step, which is considered a clear limitation in terms of convenience.
For this reason, quick-unlock systems have been developed that use quick-unlock elements. They all share the basic principle of bridging or shortening the comparatively long unlocking cycle of the locking lever and/or central locking lever in that the quick-unlock element allows the mechanical opening of the associated motor-vehicle door latch practically immediately following actuation of the drive.
In particular, German 102 47 842 provides that shifting of the central locking arrangement from the locked to the unlocked state initially moves the linkage and/or linkage arrangement from the locked into the unlocked state and thereafter moves the inside locking element from the locked to the unlocked state. For this purpose, a quick-unlock lever is provided, the locking lever and the quick-unlock lever being moved to the unlocked and locked states by means of the drive. The quick-unlock lever is connected to the linkage arrangement, specifically via a link rod.
The known configuration has proven useful in principle, however it has an overall uninviting design because the quick-unlock lever is mounted on the locking lever and/or both pivot about the same axis. In addition a custom locking lever is needed for the quick-unlock function.
A similar system is seen in EP 1 288 408. This system offers a further development in that the quick-unlock lever releases the latch mechanism during the course of the quick-unlock operation with the help of the drive, substantially independently of the position of the locking lever. The quick-unlock lever is configured as a one-arm lever that is pivoted on the locking lever.
In the system of EP 1,283,934 [U.S. Pat. No. 6,737,758], the quick-unlock element can be connected to the lock mechanism and/or a locking element in a more or less integral manner. In an alternative system, the quick-unlock element can be configured as a spring-loaded snap-action element that is released by the drive and snaps into its actuation position under spring force.
A motor vehicle door lock of the kind described above is the subject matter of EP 1 283 934 B1. Here, the quick-unlock element is associated with the central locking drive. In particular, the quick-unlock element is configured as a spring a spring-loaded snap-action element that is only released by the central locking drive and then snaps into its actuating position under spring force. This design is relatively complex because the lock mechanism and the central locking drive are separate units.